This is an optional Kyosho 91mm HD CV Swing Shaft Set, and is intended for use with the Kyosho MP9 TK13 1/8 scale buggy, as well as previous MP9 models. These shafts are made to be "heavy duty" providing extra strength and durability than the previous generation CV shafts. These will also work in the front and rear positions when the vehicle is in the narrow track width. If the rear end is setup for wide track it is recommended to use the 93mm HD CV Set (KYOIFW433).